Fluid cooling for electron emission tubes



June 19, 1934. H. E. HALLBORG FLUID COOLING FOR ELECTRON EMISSION TUBES Filed March 17, 1927 INVENTOR HENRY E. HALLBORG 89 P TORNEY Patented June 19, 1934' FLUID COOLING FOR ELECTRON EMISSION TUBES Henry E. Hallborg, Montclair, N. J., assignor to Radio Corporation of America, a corporation of Delaware Application March 1'7, 1927, Serial No. 175,983 59 Claims. (01.250 17) This invention relates to communication equipment and more particularly to such equipment employing electron emission tubes requiring cooling by means of a circulating fluid.

5 Water or other fluid cooling of electron emission tubes is necessary for large power outputs, and this cooling is applied to the tube anode. Since the anode is at high potential, whereas the water is ordinarily at ground'potential and some- I what conductive, the latter becomes a resistance shunt across the tube and there results a loss of radio frequency energy.

This high resistance shunt is also objectionable because it is in parallel with the tuned output circuit and therefore broadens the tuning of that circuit. It is still further objectionable for the reason that sparking frequently occurs between parts of the rubber hose employed to feed the cooling water, thereby charring the hose and ultimately causing serious leaks.

It is an object of my invention to obviate the above defects in present arrangements, and this I propose to do, broadly, by applying the cooling fluid to a part of the transmitter equipment which is always at zero alternating potential, and thence to convey it, together with the electrical energy, to the tube anodes.

More specifically, I propose to use the output inductor of each transmitter stage as a conduit for carrying the cooling fluid to the anode of the tube. In other words, the output inductor is flow connected as well as electrically connected to the anode of the tube. To do this the inductor is made by winding a conduit-conductor. In the case of a push-pull stage the mid-point of the output inductor is at zero alternating potential, and it is at this point that I feed the cooling fluid into the conduit-conductor. arranged for push-pull amplification, but instead employs a single tube without a divided output coil for neutralization thenthe cooling fluid simply is flow connected to the end of the output inductor.

The specification is accompanied by a drawing in which i Figure 1 is a wiring diagram of a push-pull stage showing the electrical efiect of the cooling water conduits 'as previously arranged;

Figure 2 is a similar diagram in accordance with my improved arrangement;

Figure 3 is a schematic drawingrepresenting an arrangement using a single inductor;

Figure 4 is a drawing showing a modification employing two inductors arranged in series; and

It the stage-is not Figure 5 is a fragmentary profile of the arrangement in Fig. 4.

Referring now to Figure 1, the two tubes of a push-pull stage are indicated at 2 and 4. The output circuitof the stage consists of the inductor 6 and the variable condenser 8, and is connected to' the two tube anodes 10 and 12. The cooling water, being in contact with the tube anode and with the ground, forms high resistance paths 14 and 16 which shunt a part of the high frequency energy, and therefore cause undesirable losses. The potential applied across resistances l4 and 16 is the radio frequency potential,- which may be of the order of fifteen or twenty thousand volts, and also the direct potential from the source 18. 7

It is clear that at the mid-point M of the inductor 6 the radio frequency potential is always zero, for while the potential at the ends of the' coil fluctuate between positive and negative maxima they are at any instant of opposite polarity, and the potential distribution is such that there always is zero value at the mid-point M. According to my inventionthe coolingwater is introduced at the point M, and as may be seeri in Figure 2, in this case it forms a resistance path 22 which is in shunt with only the direct current supply. The resistance is connected across a potential of 'much lesser value, and has the fur-. ther advantage of serving to steady out fluctuations in the direct current supply. With reIer- 86 ence to the high frequency potential both ends of the resistance are at ground or zero value.

Referring now to Figure 3, the electron emission-tubes 2 and 4 have. their anodes 10 and 14 immersed'in cooling water contained in the jack- 90 ets 30 and 32, each of which has an inlet nozzle 34 and an outlet nozzle 36. As illustrated in Fig. I 3 the tuning inductor 6 is formed, most simply, of two copper tubes 38 and 40 which are continuously wound together to form, electrically. a single inductance. As shown in Figure 3, the axis of the coil system 6 isperpendicular to the axis of the cylindrical water jackets or fluid cooling chambers for the tubes 2, 4. 1 At the ends of the inductor the tubes are separated and connected respectively to the inlet and outlet nozles. At the mid-point M the feeder tubes 42 and 44 are electrically and flow connected to the tubes 38 and 40, and at a distance of at least one diameter from the coil an electrical connection 46 is made between them and the source of energy 18. Beyond this there are connected to the tubes 42 and 44 the rubber pipes 48 and 50, which run to a reservoir and to any circulating medium, for

example, a centrifugal pump.

and have their anode terminals directly connected to the fixed plates 60, 62 of an output-circuit tuning condenser. This condenser further comprises the movable plates 64, 66, which are adjustably separated by suitable mechanism 100, 102, 104 to positions nearer to or further from the fixed plates 60, 62. As in Figure 3 the inductor is wound of conduit-conductors 38 and 40, and to these the inlet and outlet'rubber tubes 48, 50 are connected at points which are at substantially zero alternating potential. The high potential ends of the inductor 6, 6' are electrically and flow connected to the tube jackets and anodes.

For either modification it is clear that while the conduit-conductors 38 and 40 are bifilar as conduits for the cooling water yet both together are but a single conductor with respect to the electrical energy. They not only may but preferably should be in contact with one another. It is also feasible to use a single tube having more than one passage through it to act as the conduits for the supply and return of the cooling water.

By reason of the cooling water flow thru the conductor it remains at a constant temperature, whereby its impedance is kept constant, and tuning is made more stable.

In the claims which follow I shall by the term circulate mean, broadly, to set a cooling fluid in motion, rather than that there shall be a closed path of motion. I employ the term conduitconductor to include broadly any conduit for a fluid which is also efficiently conductive for electricity. By inductor I means inductive reactive means. Vacuum tube" is used synonymously with electron emission tube.

The mid-point M of applicants coil 6 is, as already pointed out, at zero alternating radio frequency potential. In other words, it is the minimum radio frequency potential point, a radio frequency voltage nodal point, and is the electrical center of coil 6. This point M is, of course, fixed, defined or established by the connection of the generator 18 thereto as shown in Figure 2 although it exists independently of the external circuits connected to the coil 6.

Output energy as is customary, is derivedfrom the circuits shown by inductively coupling a load circuit (not shown) to the output cooled inductor coil 6. The potential source 18 forms, of course, an impedance path from the point M to ground as does also the cooling water connections. This has been indicated in Figure 2 by the-resistor 22.

The foregoing description is by way of illustration and. not limitation of my invention, which I claim is:

1. Themethod of preventing losses of high frequency electrical energy when applying a cooling fiuid'which is at zero high frequency alternating potential to an element which is not at zero alternating potential which includes causing the fluid to take a path of flow which is so inductive that the potential drop across the path at the working frequency equals the potential of the said element.

2. In radio communication with transmission equipment having fluid cooled electron emission tubes, the method of preventing deleterious effects upon the transmission equipment caused by alternating current flow in the external cooling fluid circuits, which consists in applying the cooling fluid to a part of the equipment which is at substantially zero alternating potential, and thence causing the fluid flow to identically follow the alternating current flow with no potential difference therebetween.

3. A high frequency impedance comprising conductive tubing wound unifilar with respect to the flow of electrical energy and bifilar with respect to the fiow of fluid therethru.

4. The combination with an electron emission tube including an anode and a cooling jacket which has an inlet and an outlet for a cooling fluid, of an inductor comprising a wound conductor structurally formed into a plurality of conduits for the cooling fluid, one of said conduits being flow connected to said inlet, another of said conduits being flow connected to said out let, and said entire conductor being electrically connected to the anode.

5. A push-pull power stage including two fluid cooled electron emission tubes having anodes, a tuning coil consisting of a wound conduit-conduc tor connected between said anodes, a source of direct anode current which is electrically connected to the mid-point of said coil, and a source of cooling fluid which is flow connected to the electrical mid-point of said coil so as to be at Zero alternating potential, and which is electrically insulated therefrom except for the path created by the cooling fluid itself.

6. A push-pull power stage including first and second fluid cooled vacuum tubes each having an anode and a cooling jacket with an inlet and an outlet for a cooling fluid, and an inductor comprising first and second inductances each having a high and low potential end and each wound of a conductor structurally formed into inlet and outlet conduits for the cooling fluid, the inlet and outlet conduits of said first and second inductances being flow connected respectively to the inlets and outlets of said first and second vacuum tube jackets, the high potential ends of the first and second inductances being electrically connected respectively to the first and second vacuum tube anodes, means to electrically connect the low potential ends of said inductances, and means to fiow connect the low potential ends of said inductances with a source of-cooling fluid.

7. In combination, a pair of electron discharge devices, each having anode, cathode and control electrode elements, a tubular coil connecting an element of one of said devices with an element of the other of said devices, and means for supplying cooling fluid to the tubular coil at a point intermediate its ends.

8. In combination, a pair of physically independent electron discharge devices, a tubular coil connecting an element of one of said devices with an element of the other of said devices, and means for supplying cooling fluid to the tubular coil at a point substantially at the electrical center thereof.

9. In a high frequency electrical circuit, a continuously wound tubular inductance coil and means for supplying a cooling fluid thereto at a point intermediate its ends.

10. In a fluid cooled vacuum tube high frequency oscillation circuit, a plurality of cooled vacuum tubes, a cooled tubular inductance coil, a

fluid to flow through said coil and tubes.

11. In alternating current apparatus, an electron discharge device having a cooled electrode and a cathode,.a tubular inductance coil connected to said cooled electrode, means for supplyinga cooling fluids to the inductance coil at a point intermediate its ends, and a source of potential connected between said point and said 1 cathode.

12. A high frequency inductance system comprising in combination a continuously wound metallic member of helical form providing a double passage for the circulation of liquid and means provided at the electrical center of the inductance whereby said liquid may be admitted to said passage.

13. A high-frequency inductance system comprising a helix, said helix comprising a double passage for cooling fluids and a common passage for electrical energy.

, 14. A high frequency inductance system comprising a helix, said helix comprising a dual passage conductor for cooling fluids, a common passage for electrical energy and connecting members provided at the electrical center of said helix 'for admitting said cooling fluids.

15. In' an inductance system the combination of a helix, said helix comprising metal tubing having a double passage for the circulation of a cooling fluid and means provided at the electrical center of said helix for admitting, said fluid to said passages.

16. A high frequency inductance system com;- prising in combination a'plurality of lengths of metal tubing immediately adjacent to each other said lengths of tubing being electrically conductively connected together intermediate their ends comprising a single electrical conductor and com prising a plurality of conductors for the circulation of a liquid.

1'7. A high frequency inductance coil comprising a helical formation of metallic tubing providing a plurality of individual fluid conducting passages immediately adjacent to each other and constituting a single electrical conductor by virtue of metallic conductive connection of said tubing intermediate the ends thereof.

18. A high frequency inductance coil comprising a helical formation of metallic tubing having a plurality of individual fluid conducting passages and a single electrical passage, and fluid connecting members associated with said coil at the electrical center thereof.

19. A high frequency inductance system comprising a helical formation of metallic tubing and means for associating a cooling fluid with said tubing at the electrical center of theinductance.

20. An inductance system comprising in combination a metallic member of helical form providing a passage for the flow of liquid said system adapted to have a load circuit inductively coupled with said metallic member, an electrical circuit to ground, said circiut being connected with said metallic member intermediate the ends thereof, and means provided at the connecting point of said circuit to said member whereby said liquidmay be admitted to said passage, and means for removing said fluid after travelling through said passage and means for tuning said member ,to a desired frequency of operation.

"'21; An inductance system comprising in combination a metallic member of helical form providing a double passage for the circulation of liquid, .said member adapted to have a load circuit inductively coupled thereto, a path to ground, said path being connected with said metallic member intermediate the ends thereof and at the electrical center thereof and means provided at the electrical center of the inductance whereby said liquid may be admitted to said passage.

22. An inductance system comprising a helix, said helix comprising adouble passage for cooling fluid and a common'passage for electrical energy, a cooling fluid inlet and discharge connection along said helix and, an electrical path to ground including a source of direct current potential from a point along said helix and at the electrical center of said helix at said fluid inlet and discharge connections for maintaining the electrical potential of said helix positive with respecttogrcund.

23. An inductance-system comprising a helix, saidhelix comprising a dual passage conductor for cooling fluid, a common passage for electrical energy, means including a radio frequency path to ground coupled to a high frequency voltage nodal point at the electrical center of said helix for supplying unidirectional energy to said helix, and; a connecting member provided at the electrical center of said helix for admitting and discharging cooling fluid.

24. In an inductance system the combination of a helix, said helix comprising metal tubing having a double passage for the circulation of a cooling fluid, means provided at the electrical center of said helix for admitting said fluid 'to said pasrality of conductors for the circulation of a liquid, and an impedance path to ground for radio frequency current connected to said length of metal tubing intermediate the ends thereof at the electrical center of said tubing where the radio frequency potential at the point of admission and discharge of the liquid to the conductors is a minimum.

26. An .inductance coil comprising a helical formation of metallic tubing providing a plurality of individual fluid conducting passages immedi-- ately adjacent to each other and constituting a single electrical conductor, fluid inlet and dis charge connections for said tubing intermediate the ends' of said coil, an electrical circuit connected between said fluid inlet and discharge connections andt'he ground, said circuit including an and connected to the electrical center of said metallic tubing where there is a minimum radio frequency potential.

2'7. An inductance coil comprising a helical forimpedance path to the'radio frequency currents mation of metallic tubing having a plurality of individual fluid conducting passages and a single electrical passage, a path to ground extending between the metallic tubing and a point intermediate the ends thereof and a radio frequency impedance in said path connected to the electrical center of said coil and fluid connecting-ine'mbera associated with said coil at the electrical center thereof. P

28. A high frequency inductance system comprising ahelical formation of metallic tubing, means for associating a cooling fluid with said tubing at the electrical center of the inductance, and an electrical circuit connected to said tubing at a point intermediate the ends thereof, said circuit including a radio frequency path to ground, said path being connected to said tubing at a low radio frequency potential point at the electrical center of said tubing.

29. An inductance system comprising in combination a metallic member of helical form proriding a double passage for the circulation of cooling ii '"i, a radio frequency path connected from the electrical center of said inductance to ground, and means for admitting and discharging a cooling fluid at the electrical center of said inductance, said member being tuned for desired high frequency operation.

30. An inductance system comprising a metallic member of helical form providing a double passage for the circulation of cooling fluid, said member adapted to have a load circuit inductively coupled thereto, a reactance adapted to be electrically connected in parallel with said metallic member, means for conjointly tuning said metallic member and said reactance, a radio frequency path to ground connected to said metallic member intermediate the ends thereof and at the electrical center of said metallic member, and fluid inlet and discharge connections for said metallic member at the electrical center thereof.

31. A high frequency inductance system comprising in cor'bination a metallic member of helical form providing a double passage for the circulation of cooling fluid, a reactance conductively coupled with said metallic member of helical form, means for conjointly tuning said reactance and said member, means including a radio frequency path to ground connected to the electrical center of said metallic member at a minimum radio frequency potential point thereon and means for introducing cooling fluid at the minimum radio frequency potential points along said metallic member,

32. A high frequency inductance system comprising in combination a metallic member of helical form providing a double passage for the circulation of cooling fluid, a reactance conductively connected with said metallic member, means for conjointly tuning said reactance and said member, a radio frequency path to ground connected to the electrical center of said metallic member where there is a minimum of radio frequency potential and means for introducing and discharging cooling fluid from said metallic member at said position of minimum radio frequency potential at the electrical center thereof.

33. An inductance system comprising in combination a metallic member of helical form pro-' viding a double passage for the circulation of cooling fluid, a radio frequency path connected from the electrical center of said inductance to ground, and, means for admitting and discharging cooling fluid at the electrical center of said inductance.

34. In combination, a pair of electron discharge devices each having an anode, a fluid cooling jacket about each of said anodes, a tubular inductor electrically and .fluid flow interconnecting said jackets, said inductor being tuned for desired high frequency operation, means for supplying cooling fluid to a point intermediate saiu tubular inductor whereby said cooling fluid flows through said inductor and to said jackets, and means for removing said cooling fluid from said jackets.

35. In combination, a pair of physically distinct electron discharge devices each having its own anode and its own cathode and a fluid cooling jacket aboutsaid anodes, a hollow tubular metallic inductor connected between said jackets said inductor being tuned for desired high frequency operation, a source of cooling fluid, means for conducting said cooling fluid to substantially the mid-point of said hollow inductor whereby said cooling fluid flows through said inductor and into said jackets, and means for removing said cooling fluid from said jackets.

36. In combination, a pair of electron discharge devices each having an anode and a fluid cooling jacket about said anode, a hollow metallic inductor connected between said jackets, means for feeding cooling fluid to a point intermediate the ends of said inductor, another tubular hollow metallic inductor connected between said jackets, said inductors being tuned for desired high frequency operation and means for removing cooling fluid from substantially the center of said last mentioned hollow tubular metallic inductor.

37. In combination, a pair of electron discharge devices each having an anode and a fluid cooling jacket thereabout, means for supplying cooling fluid to said jackets, a tubular inductor interconnecting said jackets said inductors being tuned for desired high frequency operation, and means for removing cooling fluid from a point intermediate the ends and substantially at the center of said tubular inductor.

38. An inductance system comprising a helix, said helix comprising a double passage for cooling fluid and a common passage for electrical energy, a cooling fluid inlet and discharge connection along said helix and means, including a source of potential comprising a radio frequency path to ground from a point along said helix said point being the electrical center of said helix said center being located at said'fluid inlet and discharge connections, for impressing a positive potential upon said helix, said helix be ing tuned to substantially a desired radio frequency.

39. An inductance system comprising a helix said helix comprising a dual passage conductor forcooling fluid, a common passage for electrical energy, a radio frequency path to ground connected to the voltage node on said helix, 9. connecting member provided at the electrical center of said helix for admitting and discharging cooling fluid, and means for tuning said helix.

40. Aninductance system comprising in combination a plurality of lengths of metal tubing immediately adjacent to each other comprising a single-electrical conductor and comprising a plurality of conductors for the circulation of a liquid, a path to ground including a source of direct cur rent potential connected to said lengths of metal tubing intermediate the ends thereof and at the electrical center of said tubing and, means comprising a variablecondenser for tuning said tubing.

41. An inductance coil comprising a helical formation of metallic tubing providing a plurality of individual fluid conducting passages immediately adjacent to each other and constituting a single electrical conductor, fluid inlet and discharge connections for said tubing intermediate the ends of said coil, an electrical circuit connected between said fluid inlet and discharge connections and the ground, said circuit including a source of direct current potential operating to maintain said tubing at a positive potential, means for tuning said tubing and a pair of pipes of insulating material for feeding to and removing from said inlet and discharge connections, cooljacket therefor, a hollow tubular metallic induc-.

tance coil electrically and fluid flow connecting said cooling jackets together, and a substantially straight metallic pipe flow connected to said tubing at a point intermediate its ends, asource of anode potential and means for connecting said anode source to a point on said pipe away from said coil distant at least one diameter therefrom whereby anode potential is fed from said source through said pipe through said tubular helical coil through said jackets to said anodes.

44. In combination, a pair of electron discharge devices each having an anode, a fluid cooling jacket for each of said anodes, a helical coil system comprising a pair of metallic passages fluid flow and electrically interconnecting said jackets and therefore said anodes, linear inlet and outlet pipes connected to said passages said pipes being of metallic material, additional pipes of insulating material fluid flow connected to said inlet and outlet pipes, means for causing circulation of cooling fluid throughout said pipes, helicalpassages and jackets, and means for supplying anode potential'to saidanodes, said last mentioned means being electrically connected to a point on said metallic inlet and outlet pipes distant away from said coil at least one diameter thereof.

45. A push pull power stage comprising a condenser having a pair of fixed plates, and a movable plate system for varying the efiective capacity between said fixed plates, an electron discharge device having a fluid cooling jacket mounted upon each of said fixed plates, a hollow tubular inductor connected to each of said jackets, a substantially low resistance connection interconnecting the ends of said inductors removed from said jackets and means for causing the circulation of cooling fluid through said inductors and jackets, said condenser cooperating with said inductors to form a tunable high frequency electrical circuit. r

46. A push pull power stage comprising the combination of a condenser having a pair of relatively fixed plates, means for varying the effective capacity between said fixed plates, an electron discharge device having a fluid cooling jacket fixed to each of said fixed plates, an inductance comprising a metallic member of helical form providing a double passage for circulation of cooling fluid, electrically and fluid flow connected to each of said jackets, a relatively low impedance electrically connecting together the ends of said inductances remote from said jackets, and means for'causing the circulation of cooling fluid through said inductances and said jackets, said condenser and inductances forming a tunable high fre-' quency electrical circuit. a g

47., In combination, a pair of electron discharge devices each having a fluid cooling jacket, an inductance system comprising a helix having a double passage for cooling fluid connected between said jackets, a pump, a reservoir, a fluid connection comprising a. hollow conduit of insulating material connected between said pump and one of said passages, a conduit of insulating material connected between the other passage and said reservoir whereby operation of said pump causes circulation of cooling fluid through said insulating conduits and helical system, and means for applying a direct current positive potential to said helical system at the point of inlet and discharge of cooling fluid.

48. In a transmitting system employing thermionic tubes adapted to have the anodes thereof cooled by a circulating liquid, a coil of metallic tubing for conducting the circulating liquid to and from said thermionic tube, means including said coil for applying anode operating potentials to said anodes and separate cooling means connected in series with said metallic tubing for radiating heat from the circulating liquid.

49. In a transmitting system employing thermionic tubes having the anodes thereof cooled by a circulating liquid, a coil of metallic tubing for conducting the circulating liquid to and from the anodes of said thermionic tubes, a source of anode potential and means including said tubing for conducting anode potential from said source to the anodes of said tubes and heat dissipating,

means connected with said coil of metallic tubing radiating heat from said circulating liquid.

50. In a transmitting system employing thermionic tubes having the anodes thereof adapted to be cooled by a circulating liquid, coils of metallic tubing for,conducting the circulating liquid to and from said thermiohic tubes, conduits of insulation material connected in series with said coils for conveying the circulating liquid to said coils a source of high direct current anode potential and means including said coils for applying potential from said source to the anodes of said tubes.

51. In a transmitting system employing thermionic tubes having the electrodes thereof cooled by a circulating liquid, a plurality of coils of metallic tubing connected with the anodes of said tubes, a condenser connected across said coils, a source of anode potential, means including. said coils for applying potential from said source to said anodes, said coils offering a low resistance to to, and removing the liquid from, the anode of said'tube said coil having a low electrical resistance to low frequency and direct current energy a condenser connected in shunt to said coil 9. conduit of insulation material connected with said aforementioned coil for conveying the cooling liquid therefrom and means for dissipating heat from the coolingliquid conveyed from said circuit 53. A transmitting system including a high. power tube having a cathode, a control electr e and an anode, an oscillating circuit connected with said anode, means for energizing said cath-- ode, a power supply circuit for said an0de, a fluid circulating system for subjecting said anode to the effects of cooling fluid, said fluid circulating system including a supply pipe line and a discharge pipe line leading to said anode, and a pair of independent sets of conduits, one set of said conduits consisting of metallic tubing wound in the form of inductances with adjacent ends thereof connected to the power supply circuit for said anode for subjecting said anode to high potential through the circuit formed by the metallic tubing, the other set of said conduits consisting of insulation material connected in series with said aforesaid conduits and comprising means for dissipating heat in the fluid path to said aforesaid conduits.

54. In a high power transmission system, a high power electron tube having an anode adapted to be cooled by a circulating fluid, sets of independent pairs of conduits, one set of said conduits being formed by conductive tubing wound in the form of radio frequency coils and providing a' circuitous path for the cooling fluid from said anode while conductively applying high potential to said anode, the other set of said conduits being formed of insulation material.

55. In a transmitting system including a high power tube having a cathode, a control electrode, and an anode adapted to be fluid cooled, means for energizing said cathode, a source of power supply for said anode, a pair of metallic tubular coils, one of said metallic coils being connected to said anode at the fluid inlet thereof, the other of said metallic coils being connected to said anode at the fluid outlet thereof, said metallic coils forming an output coil, said source of anode power supply having its positive terminal connected to both of said metallic coils at the ends thereof remote from said anode and having its negative terminal connected to said cathode, a source of circulating cooling fluid, an insulating fluid conducting member connected to said source fluid, means for causing the circulation of cooling fluid into and out of said inductance system at points located substantially at the electrical center of said passages, a condenser coupled to said inductance for tuning said inductance to a desired frequency and, a unidirectional source of potential connected between the electrical center of said inductance system and said cathodes for maintaining said anodes positive with respect to said cathodes.

57. In combination, a pair of physically separated independent electron devices each having an anode, a cathode and a grid, a fluid cooling jacket associated with each of said anodes for removing heat therefrom, a helical inductor having a double passage for circulating cooling fluid, electrically and flow connected to each of said jackets, said helical inductors being separated and arranged so that their axes are parallel to each other, a connection having low impedance to alternating currents connecting together the ends of said inductors removed from said jackets and means for causing a circulation of cooling fluid through said inductors and jackets.

58. In apparatus of the character described, a vacuum tube having an anode, a cylindrical fluid cooling jacket about said anode, an inductance coil having a dual passage for the flow of cooling fluid, electrically and flow-connected to said jacket, one of said passages being connected to the top of said jacket and the other being connected to the bottom of said jacket, and means for causing the circulation of cooling fluid through said passages and jacket, said inductance coil being arranged so that its longitudinal axis is perpendicular to the longitudinal axis of said cylindrical fluid cooling jacket.

59. In apparatus of the character described, a vacuum tube having an anode, a cylindrical fluid cooling-jacket about said anode, an inductance coil having a dual passage for the flow of cooling fluid, electrically and flow-connected to said cylindrical jacket, one of said passages being connected to the top of said jacket and the other being connected to the bottom of said jacket, and means for causing the circulation of cooling fluid through said passages and jacket, said inductance coil being arranged so that its longitudinal axis is parallel to the longitudinal axis of said fluid cooling jacket.

HENRY E. HALLBORG. 

